tet format

The tet file format consists of one line per tetrahedron.
Each line is of the form

T:x0 y0 z0:x1 y1 z1:x2 y2 z2:x3 y3 z3:Tn

where the x-y-z triplets are the coordinates of the three corners of the
tetrahedron. The last field on the line is a letter and a number
naming the type of tile and the number of the vertex at the center of the
configuration.